SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Results of Operations for Natural Gas and Crude Oil Producing Activities (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Natural gas, NGL and crude oil sales	$ 379,796	$ 274,783	$ 304,157
Commodity price risk management	(23,905)	32,339	46,090
Total Revenues from Oil and Gas Producing Activities	355,891	307,122	350,247
Production Costs	81,365	77,537	75,717
Exploration Expense	7,071	22,605	6,289
Impairment of Oil and Gas Properties	53,438	162,287	25,159
Depreciation, Depletion and Amortization	124,202	146,879	128,458
Accretion of Asset Retirement Obligations	4,747	4,060	1,897
Gain on Sale of Properties and Equipment	3,722	(24,273)	(4,050)
Total Expense from Oil and Gas Producing Activities	274,545	389,095	233,470
Results of Operations of Natural Gas and Crude Oil Producing Activities, Income before Income Taxes	81,346	(81,973)	116,777
Provision for Income Taxes	(29,400)	31,163	(36,785)
Results of operations for natural gas and crude oil producing activities, excluding corporate overhead and interest costs	$ 51,946	$ (50,810)	$ 79,992